This invention relates generally to interlocking attachments for securing shims to backing plates, and in particular, to an improved interlocking method for ensuring improved mechanical attachment of the shim to the backing plate, and an improved assembly formed thereby.
In a brake assembly, such as a disc brake assembly, a rotatable disc rotates with the axle of a wheel to be braked. Braking subassemblies, comprising a steel backing plate and a braking pad, may be disposed on opposite sides of the disc. As the subassemblies move inwardly under the force supplied by an actuated piston and a related caliper, the inner surfaces of the braking pads are engaged in frictional, braking contact with the disc. A high pitched and undesired brake squeal noise can be produced during such braking engagement of the pads on the disc, which may be produced by vibration of the subassemblies during braking actuation.
To reduce and/or to eliminate the undesired brake squeal noise, sound (or noise) dampening members, commonly referred to as shims, have been used by both original equipment manufacturers and by brake repair shops.
The noise dampening shim constructions are preferably positioned both between the actuated piston and the back surface of the related steel backing plate and also between the caliper and the back surface of its related steel backing plate.
Unfortunately, this frictional contact can cause a torque or twisting force on the shim by the related piston or caliper producing a shearing force in the adhesive of the shim. Under the extreme conditions of heat and vibration the adhesive by itself is not sufficient to prevent dislodging of the shim from the backing plate during braking.
The inventors are aware of several embodiments that are designed to further reduce shifting of the shim during braking, some of which are described in copending application Ser. No. 10/147,684, the disclosure of which is incorporated by reference as if fully set forth herein and commonly owned by the present assignee. Added to this body of art is the invention disclosed and claimed in the aforementioned '684 application.
A desirable shim, which is preferably used in connection with the present invention, as well as the invention disclosed in the aforementioned '684 application, is commercially sold by the assignee of the present invention under the trademark DRIFTLOK™. A DRIFTLOK™ shim includes one or more extruded holes that align with corresponding aligned recesses in the back surface of the backing plate. This construction yields a very desirable reduction on the shearing motion of the shim.
The present inventors however have discovered that still further developments in the art are desirable. For example, it has been discovered that use of integrally molded pins, as opposed to staples of the type disclosed in the '684 application or described in U.S. Pat. No. 6,349,803, can achieve other and possibly further desirable results.
U.S. Pat. Nos. 6,135,244; 5,285,873 and 5,842,546 are three patents that describe what the inventors believe is relevant art. However, the constructions set forth therein are all patentably different from the invention claimed herein.
For example, U.S. Pat. No. 5,842,546 to Biswas describes the use of a plurality of pins that project from a face of a first metal plate, pass through holes in a vibration damping layer and then a second metal plate, and then are “crushed” to fasten the first and second plates together with the damping layer therebetween. However, it is significant that the pins do not directly contact the damping layer, but rather one of the metal plates.
U.S. Pat. No. 6,135,244 to Le Bris describes a noise-preventing plate secured to a plate by the use of an adhesive and a boss that is inserted through a complementary shaped window in a plate. Although the boss is described as being hammerable, the closest embodiment described therein still has a ledge or collar of the boss resting upon the corresponding edge of the opening of the noise preventing plate through which the boss is inserted, thus describing that the boss material lies above the top surface of the shim.
Lastly, U.S. Pat. No. 5,285,873 to Arbesman merely describes a disk brake friction assembly where a friction pad is affixed to a backing plate by fixation nips extending from the backing plate and through respective openings in the function pad, thus being patentably distinguishable from the claimed shim assembly.
The inventors of the present invention believe that further advancements in the art are desirable. For example, two important requirements of a shim and backing plate assembly is the need to avoid interference by the element(s) securing the shim to the backing plate. As such, it can be readily seen that the construction described in the '244 patent is less than desirable. Secondly, any resulting construction must satisfactorily address the problem of delamination of the shim from the backing plate, which the inventors believe is achieved less than satisfactorily in the cited patents. Also important is the need to have the shim be able to sit flat on the backing plate.
The present inventors have recognized that improvements to the state of the art are achievable and believes that the present invention overcomes the perceived deficiencies in the prior art patents as well as provides the objectives and advantages set forth above and below.